Thirty bacterial isolates were isolated from the gut contents of diseased/dead locust. Their pathogenicity was tested against 4th instar nymphs of desert locust, Schistocerca gregaria Forskål (Orthoptera: Acrididae). Two isolates, designated DL2 and DL6, out of thirty showed the highest insecticidal activities against locust nymphs in preliminary bracketing. They were bioassayed via leaf dip and per os techniques and toxicity was determined using SAS program. The insecticidal activity of DL6 was more than DL2, whereas LC 50 's values of 35 × 10 6 and 13 × 10 6 cfu's/ml were determined for DL2 and DL6, respectively, after 48 h of leaf-dip treatment. However, LD 50 's value of 53 × 10 6 and 26 × 10 6 cfu's/ml was determined for DL2 and DL6, respectively, after 24 h of per os treatment. The relative potencies of DL6 to DL2 were (2.6 and 2.03) folds in leaf-dip and per os treatments, respectively. Biochemical characterization was conducted, using GEN III MicroPlate™ Biolog identification system and confirmed with molecular identification via 16S rDNA gene sequencing. Nucleotide sequencing of each was submitted to a gene bank and an accession number was generated for each isolate. Obtained bacterial strains DL2 and DL6 were identified as Bacillus weihenstephanensis (KY630645) and Pseudomonas sp. (KY630649), with a similarity of 100 and 75% to B. weihenstephanensis strain PHCDB9 (NR_024697) and Pseudomonas sp. strain DSM11821 (KF417541), respectively. The tested strains proved their potential to be bio-pesticide agents involved in controlling desert locust nymphs.

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Thirty bacterial strains were successfully isolated from dead/diseased nymphs of the desert locust Schistocerca gregaria Forskal (Orthoptera: Acrididae) occurred in rearing cages at Egypt. Among them, two isolates, DL3 and DL4, showed a high biocidal activity against locust at preliminary bracketing bioassay. Molecular identification of the two bacterial isolates was carried out by sequencing the 16S rRNA gene and nucleotide blast of international GenBank, and the results showed that DL3 isolate was Bacillus cereus (KY630646) and DL4 isolate was Bacillus cereus (KY630647) with a 100% similarity with Bacillus cereus strain SZAN-2 (GU222440) and Bacillus cereus strain KPRR3 (KY556439), respectively. The insecticidal activity of both isolates against locust nymphs using leaf dipping and per os techniques proved that DL4 isolate was more efficient than DL3 and both of them have the potential to be successful biocidal agents to control desert locust.

The effect of Metarhizium acridum and four bioactive compounds (Neem, L-Glutamic acid, Schinus molle and abamectin) in sole treatments and in combination with M. acridum was studied on the mortality of 5 th nymphal instar of desert locust Schistocerca gregaria as well as the time mortality responses and the ultra-structure of females ovary. The obtained results showed that mortality in case of Metarhizium acridum treatment reached to 100% after 14 days, while in case of neem treatment the mortality reached to 60 % after 12 days, at the same time the mortality reached up to 20 % after 10 days post treatment with L-Glutamic acid, but such mortality reached to 50 % after 14 days post treatment with Schinus molle extract, finally the mortality reached to 60 % after 11 days of abamectin treatment. All the mixtures with M. acridum caused 100 % mortality by the 5 th day post treatment. However the sole treatments caused long time to kill 50 % of treated insects (LT50), where the LT50 of M. acridum was 7.261 day as the fastest treatment, while all mixtures caused accelerate in the mortality,but the best result was obtained in case of M. acridum + neem treatment which LT50 was only1.625 day.Any way there were different effects on ultra-structure of the ovary as result of treatments used. Such effects varied between changes in nucleus shape to changes and destruction of nuclus it self.

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